Iodine ions sensing based on fluorescence quenching method and hydrogel fiber doped with fluorescein

This paper presents an iodine ions fluorescence quenching sensor based on hydrogel fiber doped with fluorescein. The hydrogel fiber was made by photo-crosslinking with core-cladding structure made from PEGDA precursor solutions with different concentration. Compared with calcium alginate cladding material, this structure is less susceptible to damage and the thickness of the cladding is controllable, which significantly reduces the loss of the hydrogel fiber. Experimental results show that the loss of the cladding-free hydrogel is 1.669 dB/cm +/- 0.4 dB/cm, and the loss of the core-cladding hydrogel fiber is 0.597 dB/cm +/- 0.2 dB/cm. By analyzing the properties of different hydrogel precursor solutions before and after photo-crosslinking, a functional hydrogel fiber doped with fluorescein for measuring iodine ions with numerical aperture of 0.3932 and mode number about 17 was fabricated. The hydrogel fiber shows high coupling efficiency with PMMA plastic optical fiber. The sensor of iodine ions exhibited a linear range of 0 similar to 36 mM and the detection limit was calculated to be 26nM. The system also shows good stability and repeatability. Hydrogel fibers shows good biocompatibility and flexibility, which will have broad application prospects in biological area in the future.